init commit

engine/simulation.cpp

@@ -0,0 +1,19 @@
+#include "simulation.h"
+
+void Simulation::step(double dt) {
+    // 1. What load is the drivetrain currently reflecting back onto the crank?
+    //    TODO: this should come from a proper torque-balance solve; for now
+    //    the engine ignores it (see Engine::step's placeholder body).
+    double load_torque_nm = 0.0;
+    m_engine.step(dt, load_torque_nm);
+
+    // 2. Engine torque flows down through the transmission to the wheels.
+    double wheel_torque_nm = m_transmission.output_torque_nm(m_engine.torque_nm());
+
+    // 3. Wheel torque accelerates the vehicle.
+    m_vehicle.step(dt, wheel_torque_nm);
+
+    // 4. Resulting wheel speed reflects back up through the transmission —
+    //    next tick's load_torque_nm calculation (once real) will use this.
+    (void)m_transmission.reflected_engine_rpm(m_vehicle.wheel_rpm());
+}